The present invention relates to medical devices, and more particularly to artificial sphincters and artificial muscle patches that are based on electroactive polymers.
Millions of Americans are incontinent. Incontinence is the second most common reason for institutionalization of the elderly, generating costs of several billion dollars per year. Incontinence commonly arises from malfunction of the urethral sphincter. The urethral sphincter is an external sphincter formed about the urethra in both males and females which, when functioning normally, constricts the urethra and prevents flow of urine from the bladder, except when the bladder is voided during normal urination. Unfortunately, a spectrum of medical conditions can result in improper functioning of the urethral sphincter and lead to incontinence, including surgical injury following transurethral resection or radical prostatectomy, neurologic injury, or direct injury to the sphincter itself.
There are numerous prior art prosthetic sphincters for selectively closing and opening the urethra to prevent incontinence. These devices typically incorporate an inflatable cuff which surrounds the urethra, and which is inflated to restrict urine flow in the urethra. Examples of such prosthetic sphincters are seen in U.S. Pat. Nos. 4,222,377, and 5,562,598. These patents describe devices having an inflatable urethral cuff, a balloon reservoir/pressure source, and a pump. The cuff is typically implanted around the bladder neck in women, and around the bulbous urethra in most men. The implanted cuff functions similarly to a blood pressure cuff.
Fecal incontinence, like urinary incontinence is a debilitating condition affecting tens of thousands of Americans. Fecal incontinence in both men and women is typically caused by neurological or muscular dysfunction of the anal sphincter, and is commonly the result of trauma.
As with urinary incontinence, prosthetic sphincters for selectively closing and opening the anal canal to prevent fecal incontinence have been developed. One such sphincter, which is approved for use by the FDA, is available from American Medical Systems under the name Acticon(trademark) Neosphincter. As with the above artificial sphincters for urinary incontinence, these devices incorporate an inflatable cuff that functions similar to a blood pressure cuff and is inflated to restrict fecal flow. These devices also include a balloon reservoir/pressure source and a pump.
The above artificial urethral and anal sphincters, however, are cumbersome and limited, and complications occur in a high percentage of patents. Moreover, because the system is a pressurized system, it is vulnerable to leakage of the pressurized fluid.
These and other drawbacks of prior art artificial urethral and anal sphincters are addressed by a first aspect of the present invention, in which an artificial sphincter is provided that is based on electroactive polymers under electronic control.
Gastro-esophageal reflux disease (GERD) is a condition characterized by the reflux of stomach contents, including stomach acid, into the esophagus. Approximately 5 million people in the United States alone experience chronic GERD. Of these, approximately 60-65% suffer from lower esophageal sphincter dysfunction, which is typically characterized by a weakening of the lower esophageal sphincter.
The lower esophageal sphincter is a ring of smooth muscle at the bottom few centimeters of the esophagus. In its resting state, the lower esophageal sphincter creates a region of high pressure at the orifice to the stomach. This pressure is critical to the proper operation of the lower esophageal sphincter.
The lower esophageal sphincter opens in response to the peristaltic motion that is triggered when food or beverage enters the esophagus. After food passes into the stomach, the peristaltic motion ceases, and the lower esophageal sphincter returns to its normal resting state to prevent reflux of the stomach contents, including stomach acid, back into the esophagus.
Current treatment options for GERD include various endoscopic, laproscopic and pharmaceutically-based therapies, such as fundoplication, RF ballooning, and powerful acid suppressing pharmaceuticals such as Zantac(copyright) (ranitidine), Tagamet(copyright) (cimetidine) and Pepcid(copyright) (famotidine). While these options offer a highly focused therapeutic potential, they fail in providing a long-term cure, and are not conducive to patient comfort.
As such, the need for a more dynamic and versatile option for the long-term treatment of GERD is apparent. To that end, in another aspect of the present invention, an artificial lower esophageal sphincter is provided, which is based on electroactive polymers that are under electronic control.
Congestive heart failure is a progressive and debilitating illness. The disease is characterized by a progressive enlargement of the heart. As the heart enlarges, it is required to perform an increasing amount of work in order to pump blood with each heartbeat. In time, the heart becomes so enlarged that it cannot adequately supply blood. An afflicted patient is fatigued, unable to perform even simple exerting tasks, and experiences pain and discomfort.
Millions of Americans suffer from congestive heart failure, with economic costs of the disease having been estimated at tens of billions of dollars annually.
Patients suffering from congestive heart failure are commonly grouped into four classes (i.e., Classes I, II, III and IV). In the early stages (e.g., Classes I and II), drug therapy is the most commonly prescribed treatment. Drug therapy treats the symptoms of the disease and may slow the progression of the disease. Unfortunately, there is presently no cure for congestive heart failure. Even with drug therapy, the disease will progress. Further, the drugs may have adverse side effects.
One treatment for late-stage congestive heart failure is heart transplant. However, even if the patient qualifies for transplant and a heart is available for transplant, it is noted that heart transplant procedures are very risky, invasive, expensive and only shortly extend a patient""s life. For example, prior to transplant, a Class IV patient may have a life expectancy of 6 months to one-year. Heart transplant may improve the expectancy to about five years. Similar risks and difficulties exist for mechanical heart transplants as well.
Another technique for the treatment for late stage congestive heart failure is a cardiomyoplasty procedure. In this procedure, the latissimus dorsi muscle (taken from the patient""s shoulder) is wrapped around the heart and electrically paced synchronously with ventricular systole. Pacing of the muscle results in muscle contraction to assist the contraction of the heart during systole. However, even though cardiomyoplasty has demonstrated symptomatic improvement, studies suggest the procedure only minimally improves cardiac performance. Moreover, the procedure is highly invasive, expensive and complex, requiring harvesting a patient""s muscle and an open chest approach (i.e., sternotomy) to access the heart.
Recently, a new surgical procedure, referred to as the Batista procedure, has been developed. The procedure includes dissecting and removing portions of the heart in order to reduce heart volume. However, the benefits of this surgery are controversial, the procedure is highly invasive, risky and expensive, and the procedure commonly includes other expensive procedures (such as a concurrent heart valve replacement). Also, if the procedure fails, emergency heart transplant is essentially the only available option.
Others have used external constraints such as jackets, girdles, fabric slings or clamps to constrain and remodel the heart and reduce heart volume. See, e.g., U.S. Pat. No. 6,293,906 (citing numerous references including U.S. Pat. Nos. 5,702,343 and 5,800,528) and U.S. Pat. No. 6,095,968. In accordance with an example from the above ""906 patent, a cardiac constraint device can be placed on an enlarged heart and fitted snug during diastole; for example, a knit jacket device can be loosely slipped on the heart, the material of the jacket can be gathered to adjust the device to a desired tension, and the gathered material can be sutured or otherwise fixed to maintain the tensioning.
As an improvement upon the above and in accordance with a further aspect of the present invention, an artificial muscle patch is provided, which is based on electroactive polymers that are under electronic control. The artificial muscle patch provides cardiac constraint and, if desired, can be electrically paced (e.g., synchronously with ventricular systole) to improve cardiac performance.
According to a first aspect of the invention, an artificial sphincter is provided, which comprises: (a) a cuff that is adapted for placement around a body lumen, which cuff comprises one or more electroactive polymer actuators; and (b) a control unit for electrically controlling the one or more electroactive polymer actuators to expand or contract the cuff.
The one or more electroactive polymer actuators of the artificial sphincter can beneficially comprise (a) one or more active members, (b) a counter-electrode, and (c) an electrolyte disposed between the active member and the counter-electrode.
In some preferred embodiments, the active members are disposed upon one or more substrate layers. The active members can be provided in numerous configurations on the substrate layer(s), including nonlinear configurations that are capable of exerting force vectors along at last two axes, for instance, an S-shaped configuration. The substrate layer(s) can be insulating or conductive in nature. Where insulating, it may be preferred to provide conductive lines on the substrate layer(s) to allow electrical communication between active members and the power source.
In certain embodiments, the cuff will further comprise a barrier layer and/or a mesh layer.
The action of the artificial sphincter of the present invention can be controlled using a variety of control units, for example, (a) power source and a simple switch or (b) power source and a logic/control device such as a computer.
In some embodiments, the cuff is provided with a restoring force to bring it into an expanded or a contracted state, preferably by including at least one elastic structural element within the cuff to supply such a restoring force. For example, the artificial sphincter cuff can be provided with an elastic annular tube structure whose length increases upon a decrease in its cross-sectional diameter.
The artificial sphincters of the present invention can also comprise a sensing system (such as a system comprising strain gauges) for sensing the degree of contraction of the electroactive polymer actuators.
Opposing ends of the artificial sphincter cuffs of the present invention may be provided with fasteners for securing the cuff around the body lumen.
The artificial sphincter cuffs of the present invention may be adapted for placement around a number of body lumens, including the urethra, the anal canal, and the lower esophagus.
A lower esophageal sphincter in accordance with the present invention can be provided, for example, with sensing system that detects when food or beverage enters the esophagus, or with a sensing system that detects when the stomach is attempting to regurgitate its contents.
Other embodiments are directed to the treatment of fecal incontinence, urinary incontinence or gastro-esophageal reflux disease by implanting into a patient an artificial sphincter in accordance with the present invention.
One advantage of this aspect of the present invention is that artificial sphincters are provided, which address fecal or urinary incontinence in a patient.
This aspect of the present invention is also advantageous in that an apparatus is provided, which offers a relatively instantaneous way to empty the bladder/lower bowel.
This aspect of the present invention is further advantageous in that artificial urethral and anal sphincters are provided, which are based on electroactive polymers under electronic control. As a result, a pressurized system such as that used in the prior art, with concomitant vulnerability to leakage of the pressurized fluid, is avoided.
Another advantage of this aspect of the present invention is that an artificial lower esophageal sphincter is provided, which compensates for lower esophageal sphincter dysfunction in a patient.
Another advantage this aspect of the present invention is that a long-term cure for GERD is provided.
A further advantage of this aspect of the present invention is that an artificial lower esophageal sphincter is provided, which is based on electroactive polymers under electronic control.
According to another aspect of the present invention, an artificial muscle patch is provided, which is adapted to be implanted adjacent a patient""s heart. The artificial muscle patch comprises: (a) one or more electroactive polymer actuators; and (b) a control unit for electrically controlling the one or more electroactive polymer actuators to expand or contract the artificial muscle patch.
As above, the one or more electroactive polymer actuators of the artificial muscle patch can beneficially comprise (a) one or more active members, (b) a counter-electrode, and (c) an electrolyte disposed between the active member and the counter-electrode. In some preferred embodiments, the active members are disposed upon one or more substrate layers. The active members can be provided in numerous configurations on the substrate layer(s), including nonlinear configurations that are capable of exerting force vectors along at last two axes, for example, an S-shaped configuration. The substrate layer(s) can be insulating or conductive in nature. Where insulating, it may be preferred to provide conductive lines on the substrate layer(s) to allow electrical communication between active members and the power source. In certain embodiments, the patch will also further comprise a barrier layer and/or a mesh layer.
The action of the artificial muscle patch of the present invention can be controlled using a variety of control units, for example, (a) a power source and a simple switch or (b) power source and a logic/control device such as a computer.
The artificial muscle patch can further comprise a sensing system for detecting a patient""s heartbeat, in which case the control unit preferably paces the contraction and expansion of the electroactive polymer actuators with the heartbeat.
Alternatively, the control unit can pace both the heart as well as the contraction and expansion of said electroactive polymer actuators.
Other embodiments are directed to the treatment of congestive heart failure by implanting into a patient an artificial muscle patch in accordance with the present invention.
One advantage of this aspect of the present invention is that an artificial muscle patch is provided, which is based on electroactive polymers under electronic control.
Another advantage of this aspect of the present invention is that a device is provided, which can supply cardiac constraint and, if desired, can be electrically paced to improve cardiac performance.
A further advantage of this aspect of the present invention is that a device is provided, which can supply cardiac constraint via a procedure that is considerably less invasive and more simplified that many prior art techniques for surgically addressing congestive heart failure.
These and other embodiments and advantages will become immediately apparent to those of ordinary skill in the art upon review of the Detailed Description and claims to follow.